Living cells, the basic units of all life, are primarily water, proteins, and K; they exist in an environment containing primarily water and Na+. Components of the living cell are in constant exchange with those in the external medium. A person travelling to England is soon filled with English water, English K+--, etc., yet the traveller does not change his or her character nor identity. Thus the living being and its component cells owe their identity and uniqueness not to the molecular components themselves but to the forces and mechanisms that determine their unique composition. The theories for these forces and mechanisms are focussed on the clear segregation between living cells and their environments of the two chemically almost indistinguishable ions, K+ and Na+. According to the membrane-pump theory, cell K+ and water are free; high cell K+ and low cell Na+ result from continual pumping by energy-consuming pumps in the cell membrane. According to the association induction hypothesis, both K+ and water in cells are adsorbed, K+ singly on anionic side chains of intracellular proteins; water in multilayers by matrix proteins with extended polypeptide chains. Low solubility of large and complex molecules in this polarized water accounts for the low level of Na+, Ca++, sugar, etc., in cells. To test these theories I have chosen 5 different projects which represent either new discoveries or old ones that have long defied interpretation: (1) The reuptake of K+ and extrusion of Na+ by resealed red cell ghosts depends critically on the volume of the lysing solution. (2) The binding of K+ (and Na+) by proteins in vitro sharply increases with pH rise and the K+ or Na+ taken up exchanges with nonlabelled ions in the surrounding medium much more slowly than ions in the presence of native protein. (3) The free Ca++ concentrations to elicit contraction reported in the literature are 2 orders of magnitude apart from each other. (4) The resting potential of muscle cells can change from being cation (K+) sensitive to anion (C1-) sensitive under a variety of conditions and no good explanation has been so far established. (5) Exhaustive stimulation of frog muscles raises the osmotic activity of the cells to a level so high that it has not been possible to explain the data on the basis of conventional wisdom. These 5 projects, seemingly unconnected to one another, are major clues toward solution of the complex, but highly coherent "crossword" puzzle of the life phenomenon.